If you want to do some research yourself, read Ammianus Marcellinus' history. He was an officer in the fourth century army and personally participated in a number of wars and battles. Specifically read books 18, 23, and 24. He's not really an average man, but it might be one of the best insights you will find.

Hi there - we're happy to approve your question related to your novel, and we are happy for people to answer. However, we should warn you that many flairs have become reluctant to answer questions for aspiring novelists, based on past experience: some aspiring novelists have a tendency to try to pump historians for trivia while ignoring the bigger points they were making, while others have a tendency to argue with historians when the historical reality does not line up with what's needed for a particular scene or characterization. Please respect the answers of people who have generously given you their time, even if it's not always what you want to hear.

Additionally, as amazing as our flair panel is, we should also point out that /r/AskHistorians is not a professional historical consultation service. If you're asking a question here because you need vital research for a future commercial product such as a historical novel, you may be better off engaging a historical consultant at a fair hourly rate to answer these questions for you. We don't know what the going rate for consultancy work would be in your locality, but it may be worth looking into that if you have in-depth or highly plot-reliant questions for this project. Some /r/AskHistorians flairs could be receptive to working as a consultant in this way. However, if you wish for a flair here to do this work for you, you will need to organize this with them yourselves.